MEMS device and method of manufacturing a MEMS device

ABSTRACT

A method for manufacturing a MEMS device is disclosed. Moreover a MEMS device and a module including a MEMS device are disclosed. An embodiment includes a method for manufacturing MEMS devices includes forming a MEMS stack over a first main surface of a substrate, forming a polymer layer over a second main surface of the substrate and forming a first opening in the polymer layer and the substrate such that the first opening abuts the MEMS stack.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. application Ser.No. 15/923,599, filed on Mar. 16, 2018, which is a divisionalapplication of U.S. application Ser. No. 15/206,836, filed on Jul. 11,2016, now issued as U.S. Pat. No. 9,938,140, which is a divisional ofU.S. application Ser. No. 13/651,372, filed on Oct. 12, 2012, now issuedas U.S. Pat. No. 9,402,138 which applications are hereby incorporatedherein by reference.

TECHNICAL FIELD

The present invention relates generally to a system and a method formanufacturing a micro-electromechanical system (MEMS) device.

BACKGROUND

Over the past years a desire for smaller electronic form factors andpower consumption along with increased performance has driven anintegration of MEMS devices. In particular, MEMS microphones may becomesmaller and smaller because electronic devices such as, e.g., cellphones, laptops, and tablets become smaller and smaller.

A feature in the performance of a MEMS microphone is the size of theMEMS device itself and the stress in the MEMS microphone generatedduring the manufacturing process.

SUMMARY

In accordance with an embodiment of the present invention, a method formanufacturing MEMS devices comprises forming a MEMS stack on a firstmain surface of a substrate, forming a polymer layer on a second mainsurface of the substrate and forming a first opening in the polymerlayer and the substrate such that the first opening abuts the MEMSstack.

In accordance with another embodiment of the present invention, a MEMSdevice comprises a polymer layer, a substrate disposed on the polymerlayer and a MEMS stack disposed on the substrate. The MEMS devicefurther comprises a first opening disposed in the polymer layer and asecond opening disposed in the substrate such that the second openingabuts the MEMS stack and the first opening.

In accordance with yet another embodiment of the present invention, amodule comprises a MEMS device carrier, a MEMS device, and an adhesiveconnecting the MEMS device carrier and the MEMS device. The MEMS devicecomprises a photoresist layer, a substrate disposed on the photoresistlayer the substrate having a front side and a back side, a MEMS stackdisposed on the front side of the substrate and an opening connectingthe MEMS stack from a backside of the substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, and theadvantages thereof, reference is now made to the following descriptionstaken in conjunction with the accompanying drawings, in which:

FIGS. 1a-1i show an embodiment of a method to manufacture a MEMS device;

FIGS. 2a-2j show a further embodiment of a method to manufacture a MEMSdevice;

FIGS. 3a-3h show a yet another embodiment of a method to manufacture aMEMS device;

FIGS. 4a-4c show an embodiment of a MEMS device;

FIGS. 5a-5c show another embodiment of a MEMS device; and

FIGS. 6a-6d show yet another embodiment of a MEMS device.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The making and using of the presently preferred embodiments arediscussed in detail below. It should be appreciated, however, that thepresent invention provides many applicable inventive concepts that canbe embodied in a wide variety of specific contexts. The specificembodiments discussed are merely illustrative of specific ways to makeand use the invention, and do not limit the scope of the invention.

The present invention will be described with respect to embodiments in aspecific context, namely a silicon microphone manufacturing process.Embodiments of the invention may also be applied, however, to othermicrophone manufacturing processes or other MEMS manufacturingprocesses.

Silicon microphone wafers are typically processed on the front side toform the membrane and the backplate, and from the backside to form theback-cavity. The formation of the back-cavity requires a dry etch stepwhich is slow in time, imprecise and expensive. Conventional waferscomprise a thickness of 400 μm to 675 μm.

In one embodiment the MEMS manufacturing process comprises a thin MEMSwafer or substrate. In one embodiment a polymer layer is disposed on thethin MEMS wafer or substrate. In one embodiment a negative or positivephotoresist layer is disposed on the thin MEMS wafer or substrate. Thenegative or positive photoresist is structured and openings are formedin the negative or positive photoresist and in the substrate of the thinMEMS wafer. In one embodiment a MEMS device comprise a polymer layer, anegative photoresist or a positive photoresist layer.

An advantage is that the thin MEMS device or MEMS wafer is stabilized bythe polymer, the negative photoresist layer or positive photoresistlayer. A further advantage is that the mechanical stress in the thinMEMS device is reduced when placed on a device carrier.

FIGS. 1a-1i illustrate an embodiment of a method to manufacture a MEMSdevice. FIG. 1a shows a MEMS wafer 100 comprising a substrate no withMEMS stacks 120 disposed thereon. The substrate 110 comprises a firstmain surface or front side 111 and a second main surface or backside112. The MEMS stacks 120 comprise a membrane 121 as a top layer of thelayer stack, a backplate 123 and a sacrificial layer 122 between themembrane 121 and the backplate 123. Alternatively, the MEMS stacks 120comprise a backplate 123 as a top layer of the layer stack and amembrane 121 close to the substrate 110. The MEMS devices 105 may beMEMS microphones or silicon microphones.

In one embodiment the MEMS devices 105 may comprise transducers. Thetransducers may be sensor such as pressure sensors, accelerometers, orRF MEMS. The MEMS devices 105 may be stand-alone devices oralternatively may comprise additional devices. For example, the MEMSdevices 105 may comprise integrated circuits (ICs) or pre-amplifiers andinput/output terminals.

The substrate no may comprise a semiconductive material such as siliconor germanium, a compound semiconductor such as SiGe, GaAs, InP, GaN orSiC. Alternatively, the substrate no may comprise organic materials suchas glass or ceramic. The MEMS wafer 100 may comprise a standardthickness of 400 μm to 700 μm. FIG. 1a may show the MEMS wafer 100 afterthe front side processing has been finished.

The MEMS wafer 100 is placed or mounted on a support carrier 130. TheMEMS wafer 100 may be placed with its top surface 111 on the supportcarrier 130. The support carrier 130 may protect the MEMS stacks 120.The support carrier 130 may comprise a support substrate 134 and anadhesive layer 132. The adhesive layer 132 moves into and fills the gapsbetween the MEMS stacks 120. The support substrate 134 may be glass oran UV tape and the adhesive layer 132 may be a wax or an otherwiseadhesive material. As shown in FIG. 1b the substrate 110 of the MEMSwafer 100 is then thinned to a thickness of about 100 μm to about 200 μmor to a thickness of about 50 μm to about 200 μm. Thinning the substrate110 may be an optional step. Thinning the substrate 110 may be carriedout with an abrasive device or abrasive film.

In a next step the MEMS wafer 100 is flipped and a polymer film 140 isdisposed on the second main surface 112 of the substrate 110. Thepolymer film 140 may be a photo structurable polymer film. In oneembodiment the polymer film 140 may be an epoxy based negativephotoresist. For example, the polymer film 140 may be SU-8 resist. TheSU-8 resist comprises a chemically amplified, epoxy based negativeresist that is optically transparent and photo imageable to near UV (365nm) radiation. Cured SU-8 resist films or microstructures are veryresistant to solvents, acids and bases and have excellent thermal andmechanical stability. Alternatively, the polymer film 140 may be apositive photoresist. The polymer film 140 may be deposited or spun onthe backside 112 of the substrate 110. The polymer film 140 may comprisea thickness of about 100 μm to about 200 μm or to a thickness of about50 μm to about 300 μm.

The polymer film 140 is structured and openings 152, 154 are formed. Theopenings 152 are the pattern for cutting the substrate 110 in separateindividual pieces and the openings 154 are the pattern for the MEMSstack 105 opening. The MEMS stack openings may be a back-cavity oralternatively, a sound port of a MEMS device 105. This is shown in FIG.1 c.

In the next step shown in FIG. 1 d, the polymer film 140 is masked witha masking layer 160. The masking layer 160 may comprise a photo resist.The photo resist may be a different photo resist than the polymer film140. The masking layer 160 overlies the top surface of the polymer film140 and fills the openings 152. The masking layer 160 does not fill theopenings 154. The substrate 110 is then etched. The substrate 110 may beetched applying a directional or anisotropic etch. The substrate 110 maybe etched with a dry etch or a wet etch. For example, the substrate 110may be etched with a deep RIE. Openings 118 are formed in the substrate110. This is shown in FIG. 1 e.

The masking layer 160 is then removed from the polymer film 140. Forexample the masking layer 160 is dissolved with a stripper solvent.Alternatively, the masking layer 160 is removed with other material.Moreover, the support carrier 130 (e.g., the substrate 134 and theadhesive layer 132) is removed from the substrate 110. The supportcarrier 130 is removed by pulling or detaching the support carrier 130from the substrate 110. The resulting structure is shown in FIG. 1 f.

In the next step, shown in FIG. 1 g, the sacrificial layer 122 isremoved and the membrane 121 is released. The membrane 121 is releasedby a wet etching process. For example, the membrane 121 is released by avapor or gas phase etching with HF based etches in case the sacrificiallayer 122 is an oxide sacrificial layer. The sacrificial layer 122 isremoved such that spacers 125 remain between the membrane 121 and thebackplate 123. The spacers 123 provide the support for the membrane 121and the backplate 123.

The wafer 100 is then flipped again and placed or put on a dicingsupport 170 such that the second main surface 112 of the substrate nofaces the dicing support 170. The dicing support may be a dicing foil.The substrate 110 is then cut with a cutting device 180 through thedicing slots 152 forming cutting lines in the substrate no. In oneembodiment the cutting device 180 is a laser. The laser may melt thesubstrate 110 when cutting through the substrate. The laser 180 mayweaken the structure of the substrate 110 (but not separate it) or maycut and separate the substrate 110. Alternatively, the cutting device180 is a wafer saw. The wafer saw cut and separate the wafer in severalpieces. This is shown in FIG. 1 h.

Finally, as shown in FIG. 1 i, the dicing foil 170 may be stretched in ahorizontal direction 190 so that the individual MEMS devices 120 can bepicked up. In one embodiment, the stretching 190 of the dicing foil 170may break and separate the individual MEMS devices 120 from each other.Alternatively the stretching 190 of the dicing foil 170 may increase thespace between the MEMS devices 120.

FIGS. 2a-2j illustrate another embodiment of a method to manufacture aMEMS device. FIG. 2a shows a MEMS wafer 200 comprising a substrate 210with MEMS stacks 220 disposed thereon. The substrate 210 comprises afirst main surface or front side 211 and a second main surface orbackside 212. The MEMS stacks 220 comprise a membrane 221 as a top layerof the MEMS device layer stack, a backplate 223 and a sacrificial layer222 between the membrane 221 and the backplate 223. Alternatively, theMEMS stacks 220 comprise a backplate 223 as a top layer of the layerstack and a membrane 221 close to the substrate 210. A MEMS stack 220and a portion of the MEMS wafer form a MEMS device 205. The MEMS device205 may comprise a MEMS microphone or a silicon microphone.

In one embodiment the MEMS device 205 may comprise a transducer. Thetransducer may be a sensor such as a pressure sensor, an accelerometer,or a RF MEMS. The MEMS device 205 may be stand-alone device oralternatively may comprise an additional device. For example, the MEMSdevice 205 may comprise an integrated circuit (ICs) or a pre-amplifierand input/output terminals.

The substrate 210 may comprise a semiconductive material such as siliconor germanium, a compound semiconductor such as SiGe, GaAs, InP, GaN orSiC. Alternatively, the substrate 210 may comprise organic materialssuch as glass or ceramic. The MEMS wafer 200 may comprise a standardthickness of 400 μm to 700 μm. FIG. 2a may show the MEMS wafer 200 afterthe front side processing has been finished.

The MEMS wafer 200 is placed or mounted on a support carrier 230. TheMEMS wafer 200 may be placed with its top surface 211 on the supportcarrier 230. The support carrier 230 may protect the MEMS stacks 220.The support carrier 230 may comprise a support substrate 234 and anadhesive layer 232. The adhesive layer 232 moves into and fills the gapsbetween the MEMS stacks 220. The support substrate 234 may be glass oran UV tape and the adhesive layer 232 may be a wax or an otherwiseadhesive material. As shown in FIG. 2b the substrate 210 of the MEMSwafer 200 is then thinned to a thickness of about 100 μm to about 200 μmor to a thickness of about 50 μm to about 200 μm. Thinning the substrate210 may be an optional step. Thinning the substrate 210 may be carriedout with an abrasive device or abrasive film.

In a next step shown in FIG. 2c , the MEMS wafer 200 is flipped and anetch stop layer 240 is disposed on the second main surface 212 of thesubstrate 210. The etch stop layer 240 may be a hard mask. The etch-stoplayer 240 is patterned or selectively deposited such that the etch stoplayer 240 is not disposed on the substrate 210 in at least a centralportion of the membrane 221 or backplate 223. The etch stop layer 240may be disposed on the regions of the substrate 210 which are notvis-à-vis or opposite the membrane 221 or backplate 223. In oneembodiment the hard mask is formed by depositing an oxide such as asilicon oxide in a plasma enhanced CVD process.

In the step of FIG. 2d a polymer layer 250 is disposed on the secondmain surface 212 of the MEMS wafer 200. The polymer film 250 may be aphoto structurable polymer film. In one embodiment the polymer film 250may be an epoxy based negative photoresist. For example, the polymerfilm 250 may be SU-8 resist. The SU-8 resist comprises a chemicallyamplified, epoxy based negative resist that is optically transparent andphoto imageable to near UV (365 nm) radiation. Cured SU-8 resist filmsor microstructures are very resistant to solvents, acids and bases andhave excellent thermal and mechanical stability. Alternatively, thepolymer film 250 may be an epoxy based positive photoresist. The polymerfilm 250 may be deposited or spun on the backside 212 of the substrate210. The polymer film 250 may comprise a thickness of about 100 μm toabout 200 μm or to a thickness of about 50 μm to about 300 μm.

The polymer film 250 is structured and openings 252, 254 are formed. Theopenings 252 are the pattern for cutting the substrate 210 in separateindividual pieces and the openings 254 are the pattern for the MEMSstacks 220 opening. For example, the MEMS stack opening may be aback-cavity or a sound port of the MEMS devices 205. This is shown inFIG. 2 e.

In the next step shown in FIG. 2f , the substrate 210 is etched. Thesubstrate 210 may be etched applying a directional or anisotropic etch.The substrate 210 may be etched with a dry etch or a wet etch. Forexample, the substrate 210 may be etched with a deep RIE. Openings 218are formed in the substrate 210. The etch stop layer 240 prevents thesubstrate 210 to be etched beneath the openings 252. The openings 218are MEMS stack openings such as a back-cavity.

The support carrier 230 (e.g., the substrate 234 and the adhesive layer232) is removed from the substrate 210. For example, the support carrier230 is removed by pulling or detaching the support carrier 230 from thesubstrate 210. The resulting structure is shown in FIG. 2 g.

In the next step, shown in FIG. 2h , the sacrificial layer 222 isremoved and the membrane 221 is released. The membrane 221 is releasedby a wet etching process. For example, the membrane 221 is released by avapor or gas phase etching with HF based etches in case the sacrificiallayer 222 is an oxide sacrificial layer. The sacrificial layer 222 isremoved such that spacers 225 remain between the membrane 221 and thebackplate 223. The spacers 223 provide the support for the membrane 221and the backplate 223.

The wafer 200 is then flipped again and placed or put on a dicingsupport 260 such that the second main surface 212 faces the dicingsupport 260. The dicing support 260 may be a dicing foil. The substrate210 is then cut with a cutting device 270 through the dicing slots 252forming cutting lines in the substrate 210. In one embodiment thecutting device 270 is a laser. The laser 270 may melt the substrate 210where it cuts through the substrate 210. The laser 270 may weaken thesubstrate 210 (but not separate it) or may cut and separate thesubstrate 210. Alternatively, the cutting device 270 is a wafer saw. Thewafer saw 270 cuts and separates the substrate 210 in several pieces.This is shown in FIG. 2 i.

Finally, as shown in FIG. 2j , the dicing support 260 may be stretchedin a horizontal direction 280 so that the individual MEMS devices 205can be picked up. In one embodiment, the stretching 280 of the dicingsupport 260 may break and separate the individual MEMS devices 205 fromeach other. Moreover, the stretching 280 of the dicing support 260 mayincrease the space between the MEMS devices 205.

FIGS. 3a-3h illustrate an embodiment of a method to manufacture a MEMSdevice. FIG. 3a shows a MEMS wafer 300 comprising a substrate 310 withMEMS devices 305 disposed thereon. The substrate 310 comprises a firstmain surface or front side 311 and a second main surface or backside312. The MEMS layer stacks 320 comprise a membrane 321 as a top layer ofthe MEMS layer stack 320, a backplate 323 and a sacrificial layer 322between the membrane 321 and the backplate 323. Alternatively, the MEMSlayer stack 320 comprise a backplate 323 as a top layer of the layerstack and the membrane 321 close to the substrate 310. The MEMS device305 may be a MEMS microphone or a silicon microphone.

The sacrificial layer 322 may overly the entire substrate 310 orsubstantial portions outside the membrane 321/backplate 323. Thesacrificial layer 322 may be about 0.5 μm to about 2 μm thick.Alternatively, the sacrificial layer 322 may be about 0.5 μm to about 1μm thick.

In one embodiment the MEMS devices 305 may comprise transducers. Thetransducers may be sensors such as pressure sensors, accelerometers, orRF MEMS. The MEMS devices 305 may be stand-alone devices oralternatively may comprise additional devices. For example, the MEMSdevices 305 may comprise integrated circuits (ICs) or pre-amplifiers andinput/output terminals.

The substrate 310 may comprise a semiconductive material such as siliconor germanium, a compound semiconductor such as SiGe, GaAs, InP, GaN orSiC. Alternatively, the substrate 310 may comprise organic materialssuch as glass or ceramic. The MEMS wafer 300 may comprise a standardthickness of 400 μm to 500 μm. FIG. 3a may show the MEMS wafer 300 afterthe front side processing has been finished.

The MEMS wafer 300 is placed or mounted on a support carrier 330. TheMEMS wafer 300 may be placed with its top surface 311 on the supportcarrier 330. The support carrier 330 may protect the MEMS layer stacks320. The support carrier 330 may comprise a support substrate 334 and anadhesive layer 332. The adhesive layer 332 moves into and fills the gapsbetween the membranes 323 if there are any. The support carrier 334 maybe glass or an UV tape and the adhesive layer 332 may be a wax or anotherwise adhesive material. As shown in FIG. 3b the substrate 310 ofthe MEMS wafer 300 is then thinned to a thickness of about 100 μm toabout 200 μm or to a thickness of about 50 μm to about 200 μm. Thinningthe substrate 310 may be an optional step. Thinning the substrate 310may be carried out with an abrasive device or abrasive film from thebackside 312.

In a next step the MEMS wafer 300 is flipped and a polymer film 340 isdisposed on the second main surface 312 of the substrate 310. Thepolymer film 340 may be a photo structurable polymer film. In oneembodiment the polymer film 340 may be an epoxy based negativephotoresist. For example, the polymer film 340 may be SU-8 resist. TheSU-8 resist comprises a chemically amplified, epoxy based negativeresist that is optically transparent and photo imagable to near UV (365nm) radiation. Cured SU-8 resist films or microstructures are veryresistant to solvents, acids and bases and have excellent thermal andmechanical stability. Alternatively, the polymer film 340 may be anepoxy based positive photoresist. The polymer film 340 may be depositedor spun on the backside 312 of the substrate 310. The polymer film 340may comprise a thickness of about 100 μm to about 200 μm or to athickness of about 50 μm to about 300 μm. This is shown in FIG. 3 c.

As shown in FIG. 3 d, the polymer film 340 is then structured andopenings 342, 344 are formed. The openings 342 are the pattern forcutting lines in the substrate 310 and the openings 344 are the patternfor openings the MEMS stack 320 opening. The MEMS stack opening may be aback-cavity or a sound port of the MEMS device 305.

Then the substrate 310 is etched. The substrate 310 may be etchedapplying a directional or anisotropic etch. The substrate 310 may beetched with a dry etch or a wet etch. For example, the substrate 310 maybe etched with a deep RIE. Openings 316 and 318 are formed in thesubstrate 310. This is shown in FIG. 3 e.

In the step shown in FIG. 3 f, the MEMS wafer 300 is then flipped againand placed or put on a dicing foil 350 such that the second main surface312 faces the dicing foil 350. The dicing foil 350 may be any type ofsupport structure. For example, the dicing foil 350 may be a glass waferwith an UV tape.

The support carrier 330 (e.g., the substrate 334 and the adhesive layer332) is removed from the substrate 310. The support carrier 330 isremoved by pulling or detaching the support carrier 330 from thesubstrate 310. The resulting structure is shown in FIG. 3 g.

In the next step, shown in FIG. 3 h, the sacrificial layer 322 isremoved and the membrane 321 is released. The sacrificial layer 322 isremoved such that spacers 325 remain between the membrane 321 and thebackplate 323. The spacers 325 provide the support for the membrane 321and the backplate 323. In one embodiment the sacrificial layer isremoved by vapor or gas phase etching. For example, HF is used forsilicon oxide etching.

In one embodiment the entire sacrificial layer 322 is removed. Themembrane 321 is released at the same time as the MEMS devices 305 areseparated. The individual MEMS devices 305 are now ready for pick-up.

FIGS. 4a-4c show an embodiment of a MEMS device 400. FIG. 4a shows across-sectional view of the MEMS device 300, FIG. 4b shows a top view ofthe MEMS device 400 and FIG. 4c shows a bottom view of the MEMS device400. The MEMS device 400 may comprise the MEMS devices manufactured anddescribed with respect to previous embodiments.

The MEMS device 400 shows a substrate 410 disposed on the hard masklayer 440. The hard mask layer 440 is disposed on the polymer layer 450.A MEMS stack 420 is disposed on the substrate 410. The MEMS stack 420may comprise a top backplate 421, spacers 425 and a bottom membrane 423.The backplate 421 comprises perforation holes 428. The opening 460 inthe mask layer 440, the polymer layer 450 and the substrate 410 may be asound port.

In an alternative embodiment the MEMS stack 420 comprises a top membrane421, spacers 425 and a bottom backplate 423. The bottom backplate 423comprises ventilation holes. The opening 460 in the mask layer 440, thepolymer layer 450 and the substrate 410 may be a back volume.

The opening 460 may comprise the same diameter in the substrate 410, themask layer 440 and the polymer layer 450. The opening 460 may be acircle or oval. Alternatively, the opening 460 may comprise othersuitable geometry such as a square or a rectangle.

FIGS. 5a-5c show an embodiment of a MEMS device 500. FIG. 5a shows across-sectional view of the MEMS device 500, FIG. 5b shows a top view ofthe MEMS device 500 and FIG. 5c shows a bottom view of the MEMS device500. The MEMS device 500 may comprise the MEMS devices manufactured ordescribed with respect to previous embodiments.

The MEMS device 500 shows a substrate 510 disposed on the hard masklayer 540. The hard mask layer 540 is disposed on the polymer layer 550.A MEMS stack 520 is disposed on the substrate 510. The MEMS stack 520comprises a top backplate 521, spacers 525 and a bottom membrane 523.The backplate 521 comprises perforation holes 528. The opening 560 inthe polymer layer 550 is larger than the opening in the substrate 510.The opening 560/565 may be a sound port or back-cavity.

In an alternative embodiment the MEMS stack 520 comprises a top membrane521, spacers 525 and a bottom backplate 523. The bottom backplate 523comprises perforation holes. The opening 560 in the mask layer 540, thepolymer layer 550 and the substrate 510 may be a back volume. Theopening 560 may comprise a different diameter in the substrate 510 thanin the polymer layer 550. The openings 560/565 may be circles or ovals.Alternatively, the openings 560/565 may comprise other suitablegeometries such as squares or rectangles.

FIGS. 6a-6c show MEMS device 600 embodiments of the invention. FIG. 6ashows a cross-sectional view of the MEMS device 600, FIG. 6b shows a topview of the MEMS device 600 and FIG. 6c shows a bottom view of the MEMSdevice 600. The MEMS device 600 may comprise the MEMS devices describedwith respect to previous embodiments.

The MEMS device 600 shows a substrate 610 disposed on the hard masklayer 640. The hard mask layer 640 is disposed on the polymer layer 650.The polymer layer 650 may comprise openings or trenches 653. A MEMSstack 620 is disposed on the substrate 610. The MEMS stack 620 comprisesa top backplate 621, spacers 625 and a bottom membrane 623. Thebackplate 621 comprises perforation holes 628. The opening 660 in themask layer 640, the polymer layer 650 and the substrate 610 may be asound port.

In an alternative embodiment the MEMS stack 620 comprises a top membrane621, spacers 625 and a bottom backplate 623. The bottom backplate 623comprises perforation holes. The opening 660 in the mask layer 640, thepolymer layer 650 and the substrate 610 may be a back volume. Theopening 660 may comprise the same diameter in the substrate 610, themask layer 640 and the polymer layer 650. The opening 660 may be acircle or oval. Alternatively, the opening 660 may comprise othersuitable geometry such as a square or a rectangle. The polymer layer 650may comprise circular rings or oval rings 653, 655. Alternatively, thepolymer layer 650 may comprise other suitable geometric rings 653, 655such as a square rings or a rectangle rings.

The embodiments of FIGS. 5a-5c can be combined with the embodiment ofFIGS. 6a -6 c.

FIG. 6d shows a MEMS system, a MEMS module or an assembled MEMS system690. The MEMS module 690 comprises the MEMS device 600 attached to aMEMS device carrier 680. The MEMS device carrier 680 may be a substrate,a laminate, a ceramic or a printed circuit board (PCB). The MEMS device600 is attached to the MEMS device carrier 680 by an adhesive 670 suchas a glue, an adhesive foil or a combination thereof. An advantage ofthe MEMS module 690 is that stress is highly decoupled.

Although the present invention and its advantages have been described indetail, it should be understood that various changes, substitutions andalterations can be made herein without departing from the spirit andscope of the invention as defined by the appended claims.

Moreover, the scope of the present application is not intended to belimited to the particular embodiments of the process, machine,manufacture, composition of matter, means, methods and steps describedin the specification. As one of ordinary skill in the art will readilyappreciate from the disclosure of the present invention, processes,machines, manufacture, compositions of matter, means, methods, or steps,presently existing or later to be developed, that perform substantiallythe same function or achieve substantially the same result as thecorresponding embodiments described herein may be utilized according tothe present invention. Accordingly, the appended claims are intended toinclude within their scope such processes, machines, manufacture,compositions of matter, means, methods, or steps.

What is claimed is:
 1. A method for manufacturing microelectromechanicalsystems (MEMS) devices, the method comprising: forming a MEMS stack overa first main surface of a substrate; thinning the substrate to expose asecond main surface; forming an etch stop layer over the second mainsurface of the substrate; patterning the etch stop layer to exposeportions of the second main surface directly over the MEMS stack;depositing a polymer layer covering the patterned etch stop layer andthe exposed second main surface; forming a first opening and a secondopening in the polymer layer such that the first opening is formeddirectly over the MEMS stack; extending the first opening into thesubstrate without extending the second opening; and performing a releaseetch to form moveable components of the MEMS devices.
 2. The methodaccording to claim 1, performing the release etch comprises etching withHF based chemistry.
 3. The method according to claim 1, wherein the MEMSstack comprises a sacrificial layer disposed between a backplate and amembrane, and wherein the release etch removes all of the sacrificiallayer.
 4. The method according to claim 1, wherein the MEMS stackcomprises a sacrificial layer disposed between a backplate and amembrane, and wherein the release etch removes a substantial portion ofthe sacrificial layer leaving spacers.
 5. The method according to claim1, wherein the polymer layer is a negative photoresist.
 6. The methodaccording to claim 1, wherein the polymer layer is a positivephotoresist.
 7. The method according to claim 1, further comprisingcutting the substrate to form individual MEMS devices without removingthe polymer layer.
 8. The method according to claim 7, wherein thecutting is aligned with the second opening.
 9. A method formanufacturing microelectromechanical systems (MEMS) devices, the methodcomprising: forming a MEMS stack over a first main surface of asubstrate; from a major surface that is opposite to the first mainsurface, thinning the substrate to expose a second main surface; forminga patterned etch stop layer over the second main surface of thesubstrate, the patterned etch stop layer comprising openings that exposeportions of the second main surface directly over the MEMS stack;depositing a polymer layer covering the patterned etch stop layer andthe exposed portions of the second main surface; patterning the polymerlayer to form a first opening and a second opening in the polymer layersuch that the first opening is vertically aligned with the MEMS stack,the first opening exposing regions of the second main surface and thesecond opening exposing portions of the patterned etch stop layer; usingthe patterned etch stop layer and the patterned polymer layer as an etchmask, extending the first opening into the substrate without extendingthe second opening; and performing a release etch to form moveablecomponents of the MEMS devices.
 10. The method according to claim 9,performing the release etch comprises etching with HF based chemistry.11. The method according to claim 9, wherein the MEMS stack comprises asacrificial layer disposed between a backplate and a membrane, andwherein the release etch removes all of the sacrificial layer.
 12. Themethod according to claim 9, wherein the MEMS stack comprises asacrificial layer disposed between a backplate and a membrane, andwherein the release etch removes a substantial portion of thesacrificial layer leaving spacers.
 13. The method according to claim 9,wherein the polymer layer is a negative photoresist.
 14. The methodaccording to claim 9, wherein the polymer layer is a positivephotoresist.
 15. The method according to claim 9, further comprisingcutting the substrate to form individual MEMS devices without removingthe polymer layer.
 16. The method according to claim 15, wherein thecutting is aligned with the second opening.
 17. A method formanufacturing microelectromechanical systems (MEMS) devices, the methodcomprising: forming a MEMS stack over a first main surface of asubstrate, the MEMS stack comprising a first side mounted to the firstmain surface and an opposite second side facing away from the first mainsurface; from a major surface that is opposite to the first mainsurface, thinning the substrate to expose a second main surface;attaching a support substrate to the second side of the MEMS stack;flipping the support substrate; forming a patterned etch stop layer overthe second main surface of the substrate, the patterned etch stop layercomprising openings that expose portions of the second main surfacedirectly over the MEMS stack; depositing a polymer layer covering thepatterned etch stop layer and the exposed portions of the second mainsurface; patterning the polymer layer to form a first opening and asecond opening in the polymer layer such that the first opening isvertically aligned with the MEMS stack, the first opening exposingregions of the second main surface and the second opening exposingportions of the patterned etch stop layer; using the patterned etch stoplayer and the patterned polymer layer as an etch mask, extending thefirst opening into the substrate without extending the second opening;removing the support substrate; and after removing the supportsubstrate, performing a release etch to form moveable components of theMEMS devices; and dicing the substrate through the second opening toform individual MEMS devices.
 18. The method according to claim 17,wherein the MEMS stack comprises a sacrificial layer disposed between abackplate and a membrane, and wherein the release etch removes all ofthe sacrificial layer.
 19. The method according to claim 17, wherein theMEMS stack comprises a sacrificial layer disposed between a backplateand a membrane, and wherein the release etch removes a substantialportion of the sacrificial layer leaving spacers.
 20. The methodaccording to claim 17, wherein the dicing is performed without removingthe polymer layer.